Arrangements of this kind have obviously been the subject of prior use in West Germany. These have a Shore D hardness of about 30 for silicone elastomers according to American Society of Testing Materials Standard D2240-85 (United States), and DIN 53.505 (West Germany). The saddle strap pad is held in its lobe region by metal pad arms, which start from the nasal region of the eye rim. Thus the saddle strap pad touches neither the bridge nor the eye rim and hence has a spacing from it of several millimeters. The advantage of the saddle strap pad is the better support of the weight.
What is disadvantageous in this construction is the following:
(a) Pad arms are necessary.
(b) The pad arms must have at their ends a construction which can absorb over a large area the forces from the lobes of the saddle strap pad, yet does not spoil the softness of the saddle strap pad.
(c) A tension is certainly exerted on the limbs of the saddle strap pad. This tension causes those regions which hitherto engaged tightly around the stem of the anchorage to enlarge ovally in the direction of tension. From this pockets result, in which perspiration, dirt and skin rubbings can collect. This is unesthetic, for one thing, and can ruin the effect which can in itself be obtained by the soft pads, i.e. the skin can be severely irritated by such accumulations.
(d) Choices of very low hardness, e.g. around 20 or lower, can no longer be used, because otherwise the anchorage would at once be pulled out from the lobes and right at the start when trying on the glasses the above-mentioned oval elongations would result, so that no person would buy such a pair of glasses. Moreover, not only would the anchorages become very useless, but the tensile loading in the upper apex region of the saddle strap pad, which is there substantially thinner, would be so high that the material would tear. On this ground also only the higher Shore hardnesses can be chosen.
(e) With various materials high Shore hardnesses have the consequence that the hardness of the material becomes dependent on temperature. If the surroundings are very hot, then the Shore D hardness tends to become softer. If it is very cold, then the Shore D hardness tends to become harder. But one wants to have Shore D hardnesses which are as uniform as possible.
(f) Since the saddle strap pad has a spacing from the eye rims and from the bridge, this construction is only suitable for those glasses in which the bridge can sit relatively high. Bridges arranged lower are not possible with such a construction.
(g) Also, in the very region which is most definitive of personality, the appearance leaves something to be desired, because an observer sees there as it were a freely floating construction, in which a milky strip, i.e. the saddle strap pad, lies above the nose of the wearer of the glasses.
(h) If the inherently soft material is subjected to a mechanical stress, then the Shore D hardness still present is shifted upwards, so that one cannot make use at all of the Shore D hardness that is inherently present.